Quote Originally Posted by The Master View Post
Is 35,000mcd bright? It sounds like quite a high number.
Depends on the viewing angle.
If you've got a 35kmcd LED with a viewing angle of 170 degrees, then, yes, that's a seriously bright LED. If that same 35kmcd LED only has a viewing angle (1/2 theta) of 10 degrees, then it won't be so bright.

Can i just double check that a 4V LED will be fine running on 12V if i use PWM? The average would end up being 3V. Im sure it was someone from here who said that would work but i dont remember who.
LEDs don't run on voltage...get that idea out of your head. Yes, they need voltage...'nuff said.
It's CURRENT that makes an LED work. Yes, you have to have enough voltage to get the current required, which is why you also sometimes need a current limiting resistor. You start pumping 12v thru a single LED (unless it's rated for 12v of course), and you WILL burn it up sooner rather than later. If you've got 12v PWM running at 25% duty cycle, yes, the average would be about 3v-ish, but you're still hitting the LED with 12v. Again, if it's rated for that 12v, then I suppose you'll be fine. Otherwise, look to have a bunch of open LEDs eventually.
Do yourself a favor and get a copy of 'The Art of Electronics' and do a bit of reading. It's my 'bible', great book, will teach you a lot about a lot of stuff.